Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	$ 430	$ 447
Incurred	20	5
Settled	(40)	(45)
Accretion	22	23
Cash Flow Revisions	0	0
ARO Liability, end of period	432	430
Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	429	446
Incurred	17	5
Settled	(40)	(45)
Accretion	22	23
Cash Flow Revisions	0	0
ARO Liability, end of period	428	429
Gas treating plant and gas wells
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	1	1
Incurred	0	0
Settled	0	0
Accretion	0	0
Cash Flow Revisions	0	0
ARO Liability, end of period	1	1
Coal ash disposal areas \| Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	191	201
Incurred	0	0
Settled	(20)	(18)
Accretion	8	8
Cash Flow Revisions	0	0
ARO Liability, end of period	179	191
Gas distribution cut, purge, and cap \| Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	186	182
Incurred	17	3
Settled	(9)	(11)
Accretion	11	12
Cash Flow Revisions	0	0
ARO Liability, end of period	205	186
Asbestos abatement \| Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	42	56
Incurred	0	0
Settled	(11)	(16)
Accretion	2	2
Cash Flow Revisions	0	0
ARO Liability, end of period	33	42
Renewable generation assets
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	0
Incurred	3
Settled	0
Accretion	0
Cash Flow Revisions	0
ARO Liability, end of period	3	0
Renewable generation assets \| Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	10	7
Incurred	0	2
Settled	0	0
Accretion	1	1
Cash Flow Revisions	0	0
ARO Liability, end of period	$ 11	$ 10

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848

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Amount of asset retirement obligations incurred during the period.

+ References

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Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ References

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Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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